The present invention relates to slew rate limiters, and more particularly to a non-linear slew rate limiter for digital video signals that minimizes "ghost" images when such signals are converted to analog signals for display on a video monitor.
When digitized analog video signals are processed in the digital domain, the resulting signals often contain frequency components that are above the "Nyquist frequency limit" of one-half the sample rate. When such signals are converted back into the analog domain, the required reconstruction filter may produce large amplitude damped oscillations in the time domain in the vicinity of "forbidden" high transition rate, or slew, signals. If the resulting signals are video signals which are viewed on a video monitor, faint "ghost" images are seen to the left or right of objects that contrast sharply with their backgrounds. This phenomenon is considered undesirable, but unavoidable given the nature of the specified reconstruction filters.
What is desired is a non-linear slew rate limiter for digital signals that minimizes "ghost" images that result from high transition rates in digital video signals.